http://www.vimer.cn/2010/12/%E5%9C%A8python%E4%B8%AD%E8%8E%B7%E5%8F%96%E5%BD%93%E5%89%8D%E4%BD%8D%E7%BD%AE%E6%89%80%E5%9C%A8%E7%9A%84%E8%A1%8C%E5%8F%B7%E5%92%8C%E5%87%BD%E6%95%B0%E5%90%8D.html
對於python，這幾天一直有兩個問題在困擾我:
- 1.python中沒辦法直接取得當前的行號和函數名。這是有人在論壇里提出的問題，底下一群人只是在猜測python為什么不像__file__一樣提供__line__和__func__，但是卻最終也沒有找到解決方案。
- 2.如果一個函數在不知道自己名字的情況下，怎么才能遞歸調用自己。這是我一個同事問我的，其實也是獲取函數名，但是當時也是回答不出來。
但是今晚！所有的問題都有了答案。
一切還要從我用python的logging模塊說起，logging中的format中是有如下選項的:
01 |
%(name)s Name of the logger (logging channel) |
02 |
%(levelno)s Numeric logging level for the message (DEBUG, INFO, |
03 |
WARNING, ERROR, CRITICAL) |
04 |
%(levelname)s Text logging level for the message ("DEBUG", "INFO", |
05 |
"WARNING", "ERROR", "CRITICAL") |
06 |
%(pathname)s Full pathname of the source file where the logging |
07 |
call was issued (if available) |
08 |
%(filename)s Filename portion of pathname |
09 |
%(module)s Module (name portion of filename) |
10 |
%(lineno)d Source line number where the logging call was issued |
11 |
(if available) |
12 |
%(funcName)s Function name |
13 |
%(created)f Time when the LogRecord was created (time.time() |
14 |
return value) |
15 |
%(asctime)s Textual time when the LogRecord was created |
16 |
%(msecs)d Millisecond portion of the creation time |
17 |
%(relativeCreated)d Time in milliseconds when the LogRecord was created, |
18 |
relative to the time the logging module was loaded |
19 |
(typically at application startup time) |
20 |
%(thread)d Thread ID (if available) |
21 |
%(threadName)s Thread name (if available) |
22 |
%(process)d Process ID (if available) |
23 |
%(message)s The result of record.getMessage(), computed just as |
24 |
the record is emitted |
也就是說，logging是能夠獲取到調用者的行號和函數名的，那會不會也可以獲取到自己的行號和函數名呢？
我們來看一下源碼，主要部分如下:
01 |
def currentframe(): |
02 |
"""Return the frame object for the caller's stack frame.""" |
03 |
try: |
04 |
raise Exception |
05 |
except: |
06 |
return sys.exc_info()[2].tb_frame.f_back |
07 |
def findCaller(self): |
08 |
""" |
09 |
Find the stack frame of the caller so that we can note the source |
10 |
file name, line number and function name. |
11 |
""" |
12 |
f = currentframe() |
13 |
#On some versions of IronPython, currentframe() returns None if |
14 |
#IronPython isn't run with -X:Frames. |
15 |
if f is not None: |
16 |
f = f.f_back |
17 |
rv = "(unknown file)", 0, "(unknown function)" |
18 |
while hasattr(f, "f_code"): |
19 |
co = f.f_code |
20 |
filename = os.path.normcase(co.co_filename) |
21 |
if filename == _srcfile: |
22 |
f = f.f_back |
23 |
continue |
24 |
rv = (co.co_filename, f.f_lineno, co.co_name) |
25 |
break |
26 |
return rv |
27 |
def _log(self, level, msg, args, exc_info=None, extra=None): |
28 |
""" |
29 |
Low-level logging routine which creates a LogRecord and then calls |
30 |
all the handlers of this logger to handle the record. |
31 |
""" |
32 |
if _srcfile: |
33 |
#IronPython doesn't track Python frames, so findCaller throws an |
34 |
#exception on some versions of IronPython. We trap it here so that |
35 |
#IronPython can use logging. |
36 |
try: |
37 |
fn, lno, func = self.findCaller() |
38 |
except ValueError: |
39 |
fn, lno, func = "(unknown file)", 0, "(unknown function)" |
40 |
else: |
41 |
fn, lno, func = "(unknown file)", 0, "(unknown function)" |
42 |
if exc_info: |
43 |
if not isinstance(exc_info, tuple): |
44 |
exc_info = sys.exc_info() |
45 |
record = self.makeRecord(self.name, level, fn, lno, msg, args, exc_info, func, extra) |
46 |
self.handle(record) |
我簡單解釋一下，實際上是通過在currentframe函數中拋出一個異常，然后通過向上查找的方式，找到調用的信息。其中
1 |
rv = (co.co_filename, f.f_lineno, co.co_name) |
的三個值分別為文件名，行號，函數名。(可以去http://docs.python.org/library/sys.html來看一下代碼中幾個系統函數的說明)
OK，如果已經看懂了源碼，那獲取當前位置的行號和函數名相信也非常清楚了，代碼如下:
01 |
#!/usr/bin/python |
02 |
# -*- coding: utf-8 -*- |
03 |
''' |
04 |
#============================================================================= |
05 |
# Author: dantezhu - http://www.vimer.cn |
06 |
# Email: zny2008@gmail.com |
07 |
# FileName: xf.py |
08 |
# Description: 獲取當前位置的行號和函數名 |
09 |
# Version: 1.0 |
10 |
# LastChange: 2010-12-17 01:19:19 |
11 |
# History: |
12 |
#============================================================================= |
13 |
''' |
14 |
import sys |
15 |
def get_cur_info(): |
16 |
"""Return the frame object for the caller's stack frame.""" |
17 |
try: |
18 |
raise Exception |
19 |
except: |
20 |
f = sys.exc_info()[2].tb_frame.f_back |
21 |
return (f.f_code.co_name, f.f_lineno) |
22 |
|
23 |
def callfunc(): |
24 |
print get_cur_info() |
25 |
|
26 |
|
27 |
if __name__ == '__main__': |
28 |
callfunc() |
輸入結果是:
1 |
('callfunc', 24) |
符合預期~~
哈哈，OK！現在應該不用再抱怨取不到行號和函數名了吧~
=============================================================================
后來發現，其實也可以有更簡單的方法，如下:
1 |
import sys |
2 |
def get_cur_info(): |
3 |
print sys._getframe().f_code.co_name |
4 |
print sys._getframe().f_back.f_code.co_name |
5 |
get_cur_info() |
================================================================================
另外,利用python的 inspect 模塊中的getframeinfo也可以得到.
- inspect.getframeinfo( frame [, context ])
-
Get information about a frame or traceback object. A 5-tuple is returned, the last five elements of the frame’s frame record.
Changed in version 2.6: Returns a named tuple Traceback(filename, lineno, function,code_context, index).